R/environments.R

In styler: Non-Invasive Pretty Printing of R Code

#' Work with parser versions
#'
#' The structure of the parse data affects many operations in styler. There was
#' unexpected behavior of the parser that styler was initially designed to work
#' around. Examples are [#187](https://github.com/r-lib/styler/issues/187),
#' [#216](https://github.com/r-lib/styler/issues/216),
#' [#100](https://github.com/r-lib/styler/issues/100) and others. With
#' [#419](https://github.com/r-lib/styler/issues/419), the structure of the
#' parse data changes and we need to dispatch for older versions. As it is
#' inconvenient to pass a parser version down in the call stack in various
#' places, the environment `env_current` is used to store the current version
#' *globally* but internally.
#'
#' We version the parser as follows:
#'
#' * version 1: Before fix mentioned in #419. R < 3.6
#' * version 2: After #419. R >= 3.6
#' # version 3: After #582. R >= 4.0
#'
#' The following utilities are available:
#'
#' * `parser_version_set()` sets the parser version in the environment
#'   `env_current`.
#' * `parser_version_get()` retrieves the parser version from the
#'   environment `env_current`.
#' * `parser_version_find()` determines the version of the parser from parse
#'   data. This does not necessarily mean that the version found is the
#'   actual version, but it *behaves* like it. For example, code that does not
#'   contain `EQ_ASSIGN` is parsed the same way with version 1 and 2. If the
#'   behavior is identical, the version is set to 1.
#' @param version The version of the parser to be used.
#' @param pd A parse table such as the output from
#'   `utils::getParseData(parse(text = text))`.
#' @keywords internal
parser_version_set <- function(version) {
  env_current$parser_version <- version
}

#' @rdname parser_version_set
parser_version_get <- function() {
  env_current$parser_version
}

#' @rdname parser_version_set
parser_version_find <- function(pd) {
  if (any(pd$token == "equal_assign")) 2L else 3L
}


#' The elements that are added to this environment are:
#'
#' @details
#' * `parser_version`: Needed to dispatch between parser versions, see
#'   [parser_version_set()] for details.
#' * `stylerignore`: A data frame with parse data containing tokens that fall within
#'   a stylerignore sequence. This is used after serializing the flattened
#'   parse table to apply the initial formatting to these tokens. See
#'   [stylerignore] for details.
#' * `any_stylerignore`: Whether there is any stylerignore marker. The idea is
#'   to check early in the runtime if this is the case and then if so, take
#'   as many short-cuts as possible. See [stylerignore] for details.
#' @keywords internal
env_current <- rlang::new_environment(parent = rlang::empty_env())